Atlantis is the last of three remaining operational orbiters in NASA's Space Shuttle fleet. In February 2011, Space Shuttle Discovery was the first of the three to launch on its final mission after nearly 30 years of space travel. Then, in April 2011, Space Shuttle Endeavour was set to launch, but was delayed due to a broken set of heaters. It took off on its final mission in mid May instead.

Now, NASA's Space Shuttle fleet will be three-for-three as Atlantis blasts into orbit for its last mission as well.

Space Shuttle Atlantis first flew into space on mission STS-51-J in October 1985. It has completed 32 missions, spent 293 days in space, carried 191 crews and has traveled 120,650,907 miles. Atlantis is the only orbiter that cannot draw power from the International Space Station while docked there. Instead, it must provide its own power for fuel cells.

Today marks Atlantis' 33rd and final mission, STS-135. It will be a 12-day mission to the International Space Station with the purpose of delivering supplies and spare parts, which will be contained in the Raffaello multipurpose logistics module.

"That is the most beautiful vehicle we've had to fly in space, ever, and it's going to be a long time until you see a vehicle roll out to the pad that looks as beautiful as that," said Walheim. "How can you beat that? An airplane on the side of a rocket. It's absolutely stunning."

Space shuttle Atlantis took off at 11:29 a.m. ET from Launch Pad 39A at the Kennedy Space Center. While some reports noted that weather could be obstacle possibly causing a delay, the astronauts started boarding Atlantis around 8:00 a.m. and the hatch was closed around 9:21 a.m. for flight.

Reports have estimated that the crowd gathered in the area to see the launch ranged from 500,000 to 1 million people.

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